Effects of Magnetic Field on Stability and Attainable Power of VE Amplifiers

Theory and modeling of new discovered effects of magnetic focusing field on the stability, gain, and power of VE amplifiers is presented. The RF structure and e-beam circuit parameter matrices are computed for different magnetic focusing conditions and then the self-excitation thresholds are obtained from the Determinant equations [1]. A new formulation for the RF structure gain is derived and used for the found self-excitation thresholds. It is shown for the example $K_{a}$ -band serpentine structure that the optimum magnetic focusing allows significantly greater gain and power than the conventional focusing. The methods and analysis described here are essential for achieving high power and bandwidth of RF amplifiers.